Some fuel injection systems for automotive engines have a plurality of fuel injectors each of which delivers fuel to the inlet port of an associated engine combustion chamber. In some such systems, the fuel injectors are mounted in sockets of a fuel rail which has a passage to supply fuel to the injectors; the fuel rail simplifies installation of the fuel injectors and the fuel supply passage on the engine.
When electromagnetic injectors are employed in such a system, the injectors deliver fuel to the engine in timed pulses and fuel flow is controlled by energizing the injectors at regular intervals and varying the duration of the fuel delivery pulses: when increased fuel delivery is desired, the injectors are energized for longer periods of time to increase the duration of the fuel delivery pulses; when decreased fuel delivery is desired, the injectors are energized for shorter periods of time to decrease the duration of the fuel delivery pulses.
It has been recognized, of course, that variations in the pressure of the fuel supplied to the injectors also affect fuel delivery by the injectors. Accordingly, in order to provide predictable and repeatable fuel delivery by the injectors in response to the duration of the fuel delivery pulses, a fuel pressure regulator is employed to establish the desired fuel supply pressure. The fuel is supplied to the injectors by a pump, and the pump supplies more fuel than is required by the injectors. The excess fuel is directed through a fuel pressure regulator represented, for example, by U.S. Pat. No. 3,511,270. The pressure regulator has a diaphragm which balances the pressure of the fuel supplied to the injectors with the bias of a pressure regulator spring. If the pressure of the fuel supplied to the injectors is less than the spring bias, the diaphragm positions a valve to shut off the excess fuel flow and thus increase the fuel pressure at the injectors; if the pressure of the fuel supplied to the injectors exceeds the spring bias, the diaphragm retracts the valve to discharge the excess fuel and thus reduce the fuel pressure at the injectors.